Polymerization of hydrocarbons



Patenteci June' 5, 1945 POLYMERIZATION F HYDROCARBON S Frederick E. Frey, Bartlesville, Okla., assigner to Phillips Petroleum Company, a corporation of Delaware Application September 11, 1939, Serial No. 294,377

Claims.

This invention relates to the formation of higher molecular weight hydrocarbons from oleiin hydrocarbons. More particularly it relates to the formation of hydrocarbons in the motor fuel boiling range from oleiin hydrocarbons having iive or .fewer carbon atoms per molecule by catalytic polymerization.

Certain solid, active olen polymerization catalysts, notably fullers earth, dried hydrous silica associated with hydrous alumina, solid phosphoric acids and the like have been shown to eiiect the conversion of simple oleiins almost exclusively into volatile, normally liquid hydrocarbons having low molecular weights, provided the reactions are conducted at somewhat elevated temperatures While maintaining the oleiins at a low pressure and in the gaseous state. Other olefin polymerization catalysts are also known, among which may be mentioned mixtures of aluminum chloride and other Friedel-Crafts type catalysts in combination with sodium chloride and bromide, silver chloride and other metallic halides, and aluminum chloride and other Friedel-Crafts type catalysts with polar organic compounds such as nitromethane, nitro-benzene, acetophenone and the like. Liquid catalysts such as liquid phosphoric and sulfuric acids have also been used.

It has been shown that, when used as fuel for internal combustion engines, especially those of the spark-ignition type, various hydrocarbons have quite widely different combustion and detonation characteristics. Thus, in general, oleiin hydrocarbons are less susceptible to the production of detonation in such engines than are the corresponding paraiins. However, even among one given class of hydrocarbons, such as (Cl. 26m-683.15)

the parafns for example, the various individual hydrocarbons dier widely among themselves as to their combustion characteristics. This is exemplified by the detonation characteristics of normal heptane and lso-octane (2,2,4-trimethyl pentane), the well-known standards used for evaluating detonation, the first causing detonation to a great extent and having, by definition, a. zero octane number, and the latter causing little if any detonationeven in engines of quite high compression ratios and having by definition a rating of 100 octane number. Even hydrocarbons of the same class and molecular Weight have widely dierent detonation characteristics; for instance in yone type of test engine various hydrocarbons had Widely dii-ferent ratings in detonation characteristics, as illustrated in Table I.

, Tesi.: I Datamation characteristics of some hydrocarbons Number of carbon atoms Blending octane d Commun number 3, 3dimethylpentane.. 2, 2, 3-trimethylbutane n-Octaue Most commercial processes today for converting gases to motor fuel, convert or polymerize normally gaseous olens as a group to higher molecular weight polymers. General exceptions to this treatment are the individual olens, ethylene and isobutylene. Ethylene is somewhat resistant to catalytic conversion and passes through many processes practically unaffected. However, it may enter into mixed polymerization, and will react to a certain extent with higher molecular weight olens, and thus even it is included in general group polymerization. Isobutylene has been recognized by many to be highly reactive, and it has been proposed to isolate it .from such group polymerization, or to subject it to selective polymerization. Such selective polymerization of isobutylene is not only desirable in order to remove it from otherolens with which it is associated, but its lowmolecular-weight polymers, especially the dimers and trimers, are quite valuable as constituents of premium aviation motor fuels. As can be seen from Table I, its dimers (the 2,2,4-trimethylpentenes) have excellent antidetonating qualities, and when these are non-destructively hy- ,drogenated the product (2,2,4-trimethylpentane) also has excellent antidetonating properties. This istrue of any tertiary-base olen, that is, an oleiln containing the RzC=CR'2 structure, where each R. is an alkyl group and each R' may be hydrogen or an alkyl group. When the tivo-carbon-atom oleiim are present in hydrocarbon mixtures which are to be polymerized by my process,the tertiary-base olefins, Z-methyl-lbutene and 2-methyl-2-butene, will react along with the isobutene, while the other pentenes survive for the general group polymerization.

It is also known that not only can dimer and trimer of a single olefin species be thus formed by juncture of two or three molecules through the agency of catalytic polymerization, but also that` co-dimer may be formed when two differing species such as isobutylene and n-butene are subjected in admixture to catalytic polymerization, as, for example, by the agency of sulfuric acid as catalyst. v to a degree also by reaction betweenl a simple dimer and a different species of simple olefin by replacement. These two modes of co-dimer formation maybe represented thus:

polymerization catalyst two or more species of olefins in admixture which differ in inherent reactivity and maintaining them in definite and different concentrations to be set forth, the more reactive species being inthe lower concentration. The more reactive species furthermore may be supplied in a series of increments to the catalyst whereby the desired concentration is maintained as it is consumed by. reaction.

It is an object of this invention to produce higher molecular weight hydrocarbons from olefin hydrocarbons of lower molecular weight.

It is also an object of this invention to produce motor fuels of good antidetonating characterv istics.

Another object of this invention isto produce olefin hydrocarbons in the motor fuel boiling range, which may be subjected to non-destructive hydrogenation to produce paraffin hydrocarbons having good antidetonating characteristics.

Still another object of this invention is to subject olefln hydrocarbons having five or fewer carbon atoms per molecule and of two or more species t'o a controlled polymerization, whereby the juncture of unlike species is favored and polymers other than those formed by simple doubling and trebling of simple molecules of similar species are produced in increased proportions.

It is a further object of the present invention to produce hybrid polymers or copolymers with increased efficiency.

Further objects and advantages of the invention will .be apparent from the following dis closure.

As an illustration of the relative reactivities ofa few of the normally gaseous olefins, it has been found that in the liquid phase, described in the copending application of Frey, McKinney, and Wood, Serial Number 747,964, filed October 11, 1934, now U. S. Patent 2,198,937, issued April 30, 1940, isobutylene diluted somewhat'with paraf'flns,

Co-dimer or hybrid formation occurs conveniently butanes, can be polymerized by ,means of hydrous silica associated with alumina such as the silica-alumina catalyst more completely described hereinafter, at 50 to 100 C.; the straight-chain olefin such as 2-butene, can be polymerized at 100 to 150 C.; and l-butene and propylene at 150 to 200 C. or more; whereas ethylene is not extensively converted unless a particularly active catalyst is used. The use of both high olefin concentration and high catalyst activity lower the temperatures required, and temperatures somewhat higher or lower than the ranges exemplified will, in some cases, give best results.

I have found that, when ahydrocarbon mixture containing more or less similar quantities of both straight-chain and tertiary-base olefins of low molecular weight is passed in the usual way over an olefin polymerization catalyst, in the initial optimum conditions for a particular catalyst are stage of the reaction the selective polymerization of the more reactive tertiary-base olefin is the predominant reaction. When depletion in the latter has occurred there follows polymerization which involves not only the juncture of like molecules, but also to some extent, a juncture of unlike molecules.

I have further found that it is possible to favor the formation of hybrid polymers by establishing and maintaining, in the hydrocarbon mixture in contact with a polymerization catalyst,'a relatively low concentration of the more reactive olefin or olefins, such as the tertiary-base olefins, whereby their union with their own species is discouraged, and at the same time establishing and maintaining a relatively high concentration of the relatively less reactive olefin or olefinssuch as the straight-chain olefins. Best results are obtained under superatmospheric pressures of the order of about 200 to 2500 pounds per square inch or more, 'and generally with pressures of about 750 pounds per square inch or more if liquid-phase operation, or dense-phase operation, is desired. Once a suitable pressure has been established I have found that the reaction conditions to be most controlled are the reaction temperature, the reaction time, and the mode of introduction and concentration control of the more reactive olefin species. The first two factors are closely related, and in general when higher temperatures are used shorter reaction times should be used. When using any particular catalyst, the temperature may be varied over a more or less limited range, with suitable adjustment in the reactiontime, without producing a great variation in the polymerization products. As the activity of the polymerization catalyst decreases duringuse, especially of a solid catalyst such as silica-alumina, it is possible to obtain a substantially constant conversion without too great a change in the characteristics of the product, by gradually raising the reaction temperature through an appreciable range. Since the specific somewhat dependent upon the catalyst, and since several known catalysts can be used in my process, it is more expedient and accurate to state that the time-temperature conditions should be such that the straight-chain olefin would be somewhat slowly polymerized if they were the only olefins present, but experimental exploring must be relied on for specific optimum values. In general, the temperatures will not be appreciably below 25 C., nor above 320 C., and on the whole I have found that successful operation is best carried onA between and 260 C. If liquidphase or dense-phase operation .is desired, the temperatures generally should not be allowed to exceed about 260 C. Even with pressures in excess of about 750 pounds per square inch, in the higher temperature range of around 260 C. and above, there may not be an actual liquid phase existing at the inlet portion of the reaction chamber unless large amounts of heavier hydrocarbons are present as a result of recirculating a part of the polymer-containing efliuent of the chamber and/or adding heavier, essentially inert hydrocarbons. However, even if such heavier hydrocarbons are not present to a large extent, the use of these super-critical pressures above '750 pounds, results inthe presence of a dense-phase condition which provides many of the beneficial eiects so that the tertiary-base oleiins compose not more than, and usually much less than, about 35 mol per cent of the total olefns to be polymerized and in contact with the polymerization catalyst. In other words, the molecular ratio of-unreacted straightchain to tertiary-base olefins should be at least about 2:1. However, better results can be obtainedwhen the tertiary-base olefins are less than about 16 mol per cent of the unreacted olens present, although the concentration should be above about mol per cent for eilcient operation. That iswith commercial operation of my process, the preferred range in which the ratio of unreacted straight-chain to tertiary-base -oleiins is to be kept should be between about 5:1y and 19:1, the optimum ratio being determined by adjusting concentration ratio until copolymer formation is found to be optimum or consumption of both oleiins is in the desired ratio. The number of addition points should preferably be so great that any one increment produces no more than 25 to 50% momentary increase in concentration labove the desired mean value.

The same principles of operation of a process for carrying out my invention, which will be more fully discussed hereinafter, apply also to nongtertiary-base oleflns, and infact all simple olens, regardless of structural type, providing a suitable difference in reactivity exists. Thus, normal pentenes and normal butenes may be reacted to form hybrid polymers with ethe less reactive propylene, and other suitable combinations will be evident after determining comparative reactivities.

Oleiins having less than six carbon atoms per molecule, are in the following order when listed inA accordance with increasing polymerization reactivity: `Iethylene, propylene, normal butenes, normal pentenes, isobutene, Z-methyl-l-butene, Z-methyl-Z-butene. With the exception that ethylenerequires aparticularly active catalyst, my process can'be operated to produce hybrid polymers or copolymers from any .of these olens and a less reactive one of these oleflns. However,l

as previously set forth, hybrid polymers are more readily formed, and are formed in larger amounts,

from straight-chain olens and tertiary-base olefins, because ofthe greater disparity between the types in respect to reactivity.

The desired concentration relationships of the straight-chain and tertiary-base olens can be established and maintained in a reaction mixture in one form of my process by adding a mixture which is relatively rich in tertiary-base oleiins to a hydrocarbon stream containing straightchain oleiins, flowing over a catalyst, at a number of points arranged progressively down-stream throughout the extent of a reaction zone. In general, I accomplish this in two ways, both of which are a modiiication of the general process outlined in the foregoing. In the first, it will be assumed for purposes of illustration that both the straight-chain olen or oleiins, and the tertiarybase olefin or olens, are available mixed together and associated in a single hydrocarbon stream. Such a mixture can be obtained from cracking-still gases, from the dehydrogenation, preferably catalytic, of a mixture of butanes, and from other sources. Also for purposes of illustration, it will be assumed that the reaction takes place in the presence of a solid catalyst which is in a relatively long catalyst chamber. Generally, only a portion of the hydrocarbon mixture is introduced to the chamber through the inlet of th'e chamber, additional portions being added at a plurality of points along the length of the chamber. If the initial ratio of straight-chain to tertiary-base oleiins is in the region of 1:1 at the start of the process,'appreciable amounts of' tertiary-base olens will be selectively polymerized, and the ratio will be raised, the temperature and reaction time being such that straight-chain olea suitably high value and extensive hybrid polykmerization is then eiected; That portion of the eiiluent which is not recirculated is passed to separating means directly, or it may first be passed into contact with another polymerization catalyst which polymerizes unreacted olens.

Another modification of my process may be operated to produce hybrid polymers between straight-chain olens and tertiary-,base olens which are in separate hydrocarbon mixtures or streams. .In this modication the stream containing straight-chain oleflns is passed into a catalyst chamber maintained under suitable conditions, and the stream containing the tertiary-l base olefins is added to the chamber at a plurality of points, one of which is preferably the mlet of the chamber. By the sequence of additions according to this mode of operation, a limited amount of tertiary-base ole'iin replaces that consumed between points of addition and a 'desired f high ratio of straight-chain to tertiary-base oleiln I may thus be maintained throughout the chamber =be returned. Also if desired, a portion of the stream or mixture containing the straight-chain olens may be blended with the mixture containing tertiary-base oleilns before the addition of the latter to the polymerization chamber. Instead of adding the stream containing a high concentration of tertiary-base oleflns at a plurality of points throughout the length of a single relatively long reaction chamber, aV substantiallyl equivalent result may be obviously obtained by using a number of smaller reaction chambers, arranged in'series, and adding a portion of such a stream at the inlet of each smaller chamber,vthe eilluent ofthe first chamber passing to the second, and so throughout the series.

I may also control the temperature of reaction, which tends to rise spontaneously because of the` exothermic nature of the reaction, by maintaining the stream introduced at intermediate points to the catalyst-containing passageway at a temperoffset the potential temperature rise which will be, in an insulated reaction system, approximately the value computed on the basis of -20,000 to 25,000 calories of heat evolved per gram-mol of polymer formed involving one juncture per average molecule of product polymer. The presence of inert diluent hydrocarbons, such as parailln hydrocarbons, will tend to reduce the temperature rise caused by the evolution of heat.

In one embodiment of my invention, which may be performed in the arrangement of apparatus shown diagrammatically in the accompanying figure, which forms a part of this specification, the fresh feed stock containing two or more olefins is subjected to polymerization with recircula- ,ature sufficiently below reaction temperature,` to

mixture passing through conduit 22 to separator 23. Any undesirable vapor or portion of this light material, is separated and passed from the process through conduit 24, the pressure being controlled with the aid of valve 25. By this means any lighter hydrocarbons in the system are either completely eliminated or withdrawn in controlled amounts. Condensed hydrocarbons are withdrawn from separator 23 through conduit 23 and a portion thereof may be passed to the top of fractionating column I1 as a liquid reflux through conduit 21, valve 28, pump 3l and conduit 3i.

If it is desired to subject any part of this light material to further treatment, another portion of this liquid is passed through conduit 32 and valves 32 and 33 to separating means 3l. Beparating means 34 may include any desirable number and combination of fractionating and other separating umts, such as selective solvent extraction as described and that portion of the ellluents f not returned to the catalyst may then be'passed through a second body of polymerization catalyst wherein further polymerization of unreacted olefins takes place and any of the more reactive` species which have survived the polymerizing operation in the first-mentioned chamber are polymerized together with any desired part of the less reactive olefin or olefins present. This effects an advantageous increase in total conversion effected while permitting the polymerization step employing recirculation to be conducted under conditions most conducive to hybrid polymer formation, namely, with operating conditions of time and temperature suillciently mild to permit survival of appreciable concentrations of both the more reactive and the less reactive olens.

One method of practicing my process will now bediscussed in detail in connection with the arrangement of apparatus diagrammatically shown in the accompanying figure which forms apart f this specification, and which illustrates various methods of practicing my invention.

A mixture of hydrocarbons containingl both straight-chain and tertiary-base olefin hydrocarbons of less thansix carbon atoms per molecule is introduced to the process 'underl suitable pressure through conduit Il and passes through valves II and I2, valves I3, I4, Il and I3 being closed, to the fractionating column I1 at an intermedlate point thereof. The temperature of this xnixturemay be controlled, if necessary, by passing all or any part of the mixture through temperature-control means such as heat cx-l changer Il with proper and conventional control of valves Il, I3 and I3. A fraction containing my hydrocarbons of lower molecular weight than thosefmost advantageously treated in the process. are withdrawn as vapors from the top of the col` umn through conduit 23 and pass through a cooling coll 2|, in which any condensible hydrocar- `bons are liqueiied under the existing pressure, the

tion units, whereby a separation can be effected between normally gaseous olefin and paraffin hydrocarbons. Light hydrocarbons, essentially parafilnlc in nature, are discharged from the process through conduit 35 controlled by valve 3B. If the hydrocarbons entering the process come from one or morevdehydrogenation processes, the material passing from the process through conduit 3l may be passed or recycled to such process or processes. If more than one stream of paraillnic hydrocarbons are produced by separating means 34, there may be more conduits, not shown, for the discharge of paraninic material.

The oleflns, in a purified or highly concentrated state,` pass from the separation eected by separating means '33 through conduit 31, valve 33 and conduit 39 to conduit I0 where they are mixed with a hydrocarbon stream coming from the top part of fractionating tower I1 through conduit 4I controlled by valve 42, and which will,

of course, be in the liquid phase. If the material passing through conduit 32 is sufficiently high in olefin content, a part of it may be passed directly to conduit 33 and thence to conduit I3 through conduit 31 and valve 38', valves 33 and 33 being closed, or only partially open. 'I'he material passing through conduit 4I will generally contain both paraflin and olefin hydrocarbons and will have a slightly higher average molecular weight than the olefins passing through conduit 3.1. The oleilns willfgenerally be butylenes, both straight-chain and tertiary-base, with some propylene, if that has not' all passed through conduitsV 20 and 32. If there were some amylenes introduced to the process through conduit I3, a'

quantity of amylenes not substantially exceeding this amount may also be in the stream entering conduit 30 from condit 4I. If amylenes are so present, any portion of them which it is desired to subject to polymerization may be removed from the column I'I,- along with other hydrocarbons of like and higher boiling point, froni a lower point in the fractlonating column, such as through conduit 43 controlled by valve 33'. If the hydrocarbon material entering column I1 through conduit I3 does not contain any heavier hydrocarbons, conduit 43 may be placed below conduit Ill, as will readily be understood by those skilled in the art. t

Hydrocarbons passing through conduit Il are received and compressed by pump Il and all or part are Passed through conduit ll. and valve 3l' to heat exchanger 33, and then through conduit and valve 43' and may be passed through valve 41 and conduit/4l 'to catalyst chamber Il. Nlis may be desired in connection with temperature control of the stream being passed by pump 44, all or a part may be passed through conduit 13 and valve 13 to conduit, 46, valves 45 and 46 being partially or completely closed as necessary. When desired, and as will generally be practiced, valve 41 will be so' controlled that a considerable portion of the material in conduit 46 will enter manifold through valve 49, and will then pass into catalyst chamber 50 at Various points through conduits 52 to 56 inclusive, controlled respectively by Valves 51y to 6| inclusive. If there is available a hydrocarbon mixture Whose oleiln content consists largely of tertiary-base olefins, such as would result from dehydrogenation of isobutane, such a stream may be introduced to the process at this point at a suitable temperature and pressure through conduit I9 and valve 29, passing into manifold 5|. The heat exchanger 69 is used to aid in the control of the temperature of the material passing through and being treated in the catalyst chamber 50. The extent and direction of this temperature control will not only be dependent upon the conditions `existing and desired Within the catalyst chamber 50 but also upon the amount and temperature of the material recycled by pump 65 and entering conduit 48 from conduit 63.

The eiiiuent of catalyst chamber 50 passes` through conduit 62, and a portion thereof may be diverted through conduit 63 and valve 64 and pump 65 to catalyst chamber 5U. As discussed in more detail elsewhere in this specification, the volume of hydrocarbon recycled by pump 65 will generally be equal to from 1 to l0 times the amount of hydrocarbons passed to the catalyst chamber 50 through conduits' 46 and I9. If desired, the stream passing through conduit 63 may be cooled somewhat, by means not shown, before it is introduced into the chamber 50. The material not withdrawn from conduit 62 continues on and finally passes'into fractionating column I1 at an intermediate point thereof: When the eX- tent of polymerization in chamber 50 has been quite limited, in accordance with prior discussion, there will be an appreciable amount of unpolymerized, low-molecular-'weight olens, which are easily polymerized, in the effluent of chamber 50. For this reason it may at times be desirable to submit that part of the eiliuent of chamber 50 which is not recycled, to a further polymerization of a portion of this remaining unpolymerized olenic material. This may be done by closing valve 66 and sending the stream into catalyst chamber 1U through conduit 61 and valve 68, and the eluent of chamber 1U into column I1 through conduit 1| and valve 12 and back into conduit 62, as shown.

. If it is desired to operate catalyst chamber 50 under substantially liquid-phase conditions, or supercritical conditions, but at elevated temperatures, it may be found desirable to have a fairly large amount of higher molecular weight hydrocarbons present. This object is attained in part through the recirculation of a portion of the etlluent of chamber 50 by means of pump 65. However, additional higher molecular weight material may be desired, and it may be desirable to have this material of a more paranic nature. Hydrocarbon material so desired, generally in the gasoline boiling-range and generally paraflinic, may be introduced to the process through conduit controlled by valve 16 and into conduit 39. Such paranic material may be a part or portion of the hydrogenated material discharged from the hydrogenating chamber 83 through conduit 81, as is hereinafter described. l

InV case a lhydrocarbon fraction is available which has the desired composition Without further fractionation, it may be introduced directly to the catalyst chamber through conduits 15, 40, 45 and 46, or through conduit I9. If this is done, the conduit I0 will not be used, and the only olens which will pass through conduit 4| or conduit 32, will be unreacted portions of the olens initially introduced through conduit 15 or conduit I9, which may be recycled through one or both of these conduits. With this arrangement, one

advantageous modification is to introduce a hy-ll drocarbon stream containing both normal butenes and isobutylene as from the catalytic dehydrogenation of a butane fraction, or both propylene and isobutylene such as is produced from the thermal dehydrogenation of isobutane followed by the removal of hydrogen and methane through conduit I9 at a suitable superatmospheric pressure and temperature.v In such a case, Y

the tertiary-base olens and the straight-chain olens should be present in about equimolecular amounts. In this modication the` eluent of chamber 50 will pass to fractionating columnv I1, the polymers will pass therefrom -through conduit 18, and unreacted hydrocarbons will pass therefrom through conduit 20 and conduit 32 to separating means 34. In separating means 34 a separation takes place of paraffins from olei-lns, the former being passed through conduit 35 and returned to the dehydrogenation, if desired, and a stream containing the latter is passed through conduits 31, 39 and 40, pump. 44 and conduits 45, 46 and 48 to chamber 50. These olens will comprise essentially unreacted straight-chain olens', and in this case a portion of the stream entering through conduit I 9 may be passed from manifold 5| through valve 49 into conduit 46, Where it will be mixed with the recycled straight-chain olefins and enter chamber 5I)A through valve 41 and conduit 48.

'I'he charge stock to vthe process entering through conduit IU may contain a larger quantity or proportion of tertiary-base olefins than can be most efficiently converted in catalyst chamber 5U which, if all polymerized there, would lead to the production of too much high molecular weight polymer. By properly controlling valves I2, I5 and |6, any desired portion of such charge stock may be passed through catalyst chamber 11 where some of -such tertiary-base olens are selectively polymerized, under appropriate conditions of temperature, pressure and reaction time.

High molecular Weight material introduced into fractionating column I1 through conduit and/ or conduit 62 becomes concentrated in the base of this column and is discharged therefrom through conduit 18 controlled by valve 19; It may at times be more desirable to produce an essentially parainic product, in which case polymers produced in the process may be subjected to hydrogenation. 'I'his can be done by partially or completely closing valve 19 and passing the material it is desired to hydrogenate from conduit v18 through conduit 80 and valve 8|, compressing it by pump 82 in conduit 80 to any desired hydrogenating pressure, and passing it to hydrogenating chamber 83 which .contains a suitable hydrogenating catalyst such as the-one disclosed herein. Hydrogen, or a gas containing free hydrogen, under suitable pressure is introduced into this chamber through conduit 84, and passes countercurrent to the hydrocarbons being treated therein. Gases containing or consisting of excess hydrogen are withdrawn from chamber 83 through conduit 85 and valve 86. Treated hydrocarbons, now essentially paraillnic, are' passed from the chamber 83 through conduit 81 and valve 88. The effluent of the process, passing from conduit 18 and/or conduit 81, may be subjected to further treatment, such as fractional distillation, blending and, the like. It may be desirable to hydrogenate only a part or a certain fraction or fractions of the polymer produced, in which case conventional fractionating means, not shown, may be interposed in conduit 88, and only the desired fraction sent to the hydrogenation chamber 83.

The emcient production of hybrid polymer can l be secured with conversion stocks of suitable composition without the aid of the recirculation operating or the use of column I1 to produce conver'- sion stock. Insuch a case a conversion stock containing reactive clean, such as isobutylene chamber 58,' oleflns undergoing polymerization,

and the reacted material passes therefrom by conduit 81 and valve 66 wholly to fractionator I1 wherein the polymer formed is isolated and discharged through conduit 18 and valve 18, while the unpolymerized partis discharged through conduit 20 and eventually passes from the system through conduit 85 controlled by valve 38. Examples I and III to be presented typify this mode of operation. In such a case, a portion of the material entering the process through conduit I9 may be passed through 4valve 48 into conduit I8, so that this portion will enter the inlet of the polymerization chamber 50. Although it is possible to employ such a modication without recirculation through conduit 63, such recirculation may, at times, be quite advantageously employed.

The charge stock may result from catalytic dehydrogenation, thermal treatment of gaseous hydrocarbons or may come from oil cracking processes, especially vapor-phase processes. The selection may be made of suitable parail'lns corresponding to the olefins desired as conversion stock for catalytic dehydrogenation. Thus, a mixture of substantially equal parts of normal butane and isobutane yields, upon dehydrogenation, isobutylene and butenes, which yield in the polymerization a co-dimer consisting mainly of octylenes that are particularlyv suitable after hydrogenation as an ingredient of aviation fuel.

-The presence of high molecular weight hydrocarbons, in the mixture charged to the process through conduit l0, is not necessarily'deleterious; if any such heavier material is present, such as would be present in an unstabilized cracked or reformed gasoline, or in the product of the thermal conversion of gaseous parafilns, it will become mixed with the polymers produced by the process and be discharged from fractionating column I1 more generally available and can also be well taken care of.l Excess propane will be discharged in part through conduit 24 and mainly through conduit 35. Excess butanes' will generally be discharged through conduit 35, and column I1 may .be so operated as to include some butanes in the material passing therefrom through conduit 18. If large amounts of light hydrocarbons are present in the mixture passing through conduit I0, conduit 15 or conduit I8, fractionating column I1 may consist of two or more separate but cooperative units, as will be obvious to those skilled in the art.

It will generally be preferable to use solid polymerization catalysts in the various stages of this process. Such a catalyst will be one such as the silica-alumina type catalysts more fully described herein, activated natural clays, so called "solid phosphoric acid catalysts, acidic phosphates or pyrophosphates of copper, cadmium, magnesium and other metals, or various metal halides such as ferrie chloride and bromide, zinc chloride and bromide. These latter may be deposited on supports such as clay, silica gel, pumice and the like when necessary. Such polymerization catalysts are not considered to be complete equivalents of each other. When I desire to obtain especially high yields of simple, highly branched cc-dimers which can be non-destructively-hydrogenated to produce parailin hydrocarbons which have high octane numbers and high response or susceptibility to the addition of tetraethyl lead, I prefer to use a catalyst such as the silica-alumina catalyst described herein. Thus, under conditions wherein polymerization occurs under a pressure which is substantially equal to or greater than the critical pressure of the hydrocarbon mixture and involves appreciably less than the. total amountof oleflnsrpassing through the reaction chamber, it appears that if catalysts such as solid phosphoricacids are used, the combustion characteristics, in internal-combustion engines, of the paraillns produced by non-destructive hydrogenation of the polymers, are not as desirable by chambers 11, 50 and 18 Vmay consist of two or more similar catalyst chambers, or groups of smaller chambers,` which are used oneafter another, as the catalyst becomes deactivated and it is necessary to provide fresh catalyst. In this manner continuous operation can be obtained for the process as a whole. The same willbe true in connection with the hydrogenation step.

EXAMPLE I The following data are presented as an example of one method of practicing my, invention. A catalyst comprising hydrous silica associated with alumina, and which will be spoken of as a silica-alumina catalyst, was prepared from a liquid sodium silicate of 41,a B. gravity containing 8.9 per cent NazO, 28.5 per cent S10: and 62.6 per cent H2O, and from commercial hydrochloric acid of 18 B. gravity. The sodium silicate was diluted by adding 1.5 volumes of water, and the acid was diluted with an equal volume of water. Equal volumes of these two reaulting solutions were mixed by rapidly flowing the sodium silicate solution. into the acid solution with `thorough stirring. The mixture was then allowed to stand overnight, and had set and stiffened to a nrm gel about 12 hours after mixing. The gel was broken by forcing it through a coarsel screen of about one-inch mesh, was washed for 12 hours and was then partially dried in hot air to a degree suilicient to shrink the gel only to a point where it attained suflicient rigidity to ring slightly when tumbled. It was again Washed and then treated with boiling water containing in solution about 5.5 per cent of aluminum chloride, the treatment continuing for about two hours. The treated material was then thoroughly washed until the wash water just gave a negative test for chlorides, after which it was dried and classified so that it was about 14 to 40 mesh in size. In this manner a limited amount of alumina was thoroughly and intimately incorporated with sil-l ica, forming a silica-alumina gel which was suitable as a catalyst for polymerizing olen hydrocarbons.

A hydrocarbon mixture containing propylene and butane in a molecular ratio of 1:1.86 was passed through a reaction chamber containing such a silica-alumina catlyst under the reaction conditions given in Table II. A hydrocarbon mixture containing isobutylene and butane in -a molecular ratio of 1:2.66 was added to the reaction vchamber at 14 points throughout the rer' action zone, the total amount' of this second stream added being about half the rst stream. The molecular ratio of propylene to isobutylene in the total charge was 3.721, and at no time in the reaction chamber was it less than about 1,

as a result of the multipoint method of addition. The polymer liquid, after being freed of unreacted hydrocarbons, had the composition given in Table II. Althoughl the average temperature of polymerization was a little higher than I pre- :2, fer generally to use for such a charge stock, the

predominance of polymer produced by the union of propylene and isobutylene is marked.

Only a small proportion of the polymer product was too heavy to be included in the present day, gasoline boiling range. The analysis of the polymer product, which was essentially' olenic, shows that more polymer was formed by union of one molecule of isobutylene with one molecule of propylene (producing heptenes) than was formed either from the union of two molecules of propylene or two molecules of isobutylene.

y pumice used, there was used:

A hydrogenation catalyst was prepared by forming a concentrated aqueous solution of the nitrates of nickel, 'aluminum and copper, adding ground pumice stone of 4 to 20 mesh in sizejand slowly evaporating the Water from the mixture while stirring it. For every gallon of ground Pounds N(NO3)2.6HzO 3.05 A1(NO3)3.9H2O 4.48 C'u(NO3) 2 .3H2O 0.36

After the mass of pumiceso treated had been dried, it was heated to a temperature of the order of 35o-400 C., whereby most of the nitrates were decomposed, forming the oxides. At the end of this treatment, hydrogen was passed over the material at substantially the same temperature, reducing the .oxides of nickel and copper. The nal material was an excellent catalyst for use in saturating olen hydrocarbons with hydrogen, forming paraiin hydrocarbons of essentially the same boiling characteristics, and is herein called a nickel-copper-alumina catalyst.

A polymer liquid, produced as described and boiling below 230 C., was non-destructively hydrogenated using a nickel-copper-alumina catalyst, and the olefins in the liquid were converted to the corresponding paraflins, with. practically .D35'7--34T) are given in Table III.

Example II On passing a hydrocarbon mixture of the following composition,

Weight per cent CSHG.' 7.5 Iso-04H9 19.0

C4H1o 73.5

through a bed of the silica-alumina catalyst of Example I at 180 C. while returning to the inlet continuously a volume of the eilluent stream equal to 10 times the fresh hydrocarbon mixture, polymerization is effected incompletely with respect to both propylene and isobutylene, 3.4 per cent of the former and 10.0 per cent of the latter surviving. On passing the non-returned portion of the eilluent stream through a second body of the same catalyst in simple once-through fashion, the concentrations-are reduced to per cent CzHs and 0.5 per cent iso-04H8. After separating it from the eiluents, the polymer formed, which is equivalent to the olefin disappearing, contains 33 per cent distilling above the dimer range and` 37 per cent of the total consists of branched heptenes. Upon hydrogenation-the various fractions of the total hydrogenated polymer liquid have octane numbers similar to those given for the fractions in Example I.

i Example III` Normal butenes and isobutene may be copolymerized to form hydrocarbons in thecmotor fuel boiling range, and containing predominant proportions of highly branched octanes, in the following manner. ing about 30 per cent olen hydrocarbons which are predominantly normal butenes is passed t a reaction chamber containing a silica-alumina catalyst and maintained at a temperature level between about 140 and 180 C.; under a Apressure of about 1500 pounds per square inch. A second hydrocarbon stream containing isobutylene in an amount substantially equivalent to 50% of the normal butenes in the first stream, is divided into five substantially equal portions which are passed to theo reaction chamber, one portion being mixed with the stream containing normal butenes irnmediately prior to its introduction to the catalyst chamber. The efllue-.it of the reaction chamber is cooled and passed to separating means wherein hydrocarbon polymers are separated from unreacted hydrocarbons. The octene fraction of this liquid is predominant in highly branched olens and is readily separated by fractional distillation.

The octanes produced therefrom by non-destructive hydrogenation have Aan octane number (A. S. T. M. D357-.-37T) of about 90-95, and after the addition of 1 cc. of tetraeth'yl lead per gallon, the octane number is approximately 100 or higher.

The hydrocarbon mixtures which are suitable for charge stocks are usually relatively simple in composition, and the olefins which are to be polymerized are readily identiiied' by modern analytical methods such as low-temperature fractional distillation combined with controlled acid absorption, both as to actua1 identities and as to concentrations. Likewise, the polymerization conditions are such that side reactions are at a minimum, and polymers formed can be readily analyzed by combinations of fractional distillation, both of the polymers and of the corresponding saturated Compounds produced by nondestructive hydrogenation, determination of physical properties, and by determination of combustion characteristics in well-known test engines. With such accurate testing methods possible for the simple materials involved, one skilled in the art' may readily control the process to produce optimum results for a given charge stock and polymerization catalyst, and establish suitable conditions for operation by simple trial. Likewise, when charge stocks come .from known dehydrogenation processes wherein hydrocarbon mixtures of simple compositions`are-dehydrogenated, the most desirable recycling of unreacted parans which are separated from the eilluent of the polymerization, in appropriate amounts and composition, to such a dehydrogenation, is

easily and'readily determined.

This invention is not necessarily restricted to any narrowly defined catalyst or set of operation conditions. The general rules have been given relative to these matters so that optimum results may be obtained, and when dealing with a particular charging stock or mixture oi' hydrocarbons,

anyone skilled in the art may follow the directions given herein and obtain results as shown.

I claim: f 1. A process for producing a hydrocarbon poly- A hydrocarbon stream contain-V meric product having a boilingrange within the motor-fuel boiling range from two separate and dierent oleiin hydrocarbon fractions, one oi which contains olefins that have generally morehiglily-branched structures than those contained in the other fraction, which comprises passing the fraction containing the generally less-highlyf branched olefins under reaction conditions such that copolymerization between the more-highlybranched oleiins and less-highly-branched olens takes place readily but reaction between the lesshighly-branched olefins takes place only to a minor extent over a solid polymerization catalyst in a catalyst chamber and adding, the other fraction containing the generally more-highly branched olens to said catalystV chamber at a plurality Aof successive pointsA in said catalyst chamber to react oleilns of the one fraction with olens of the other fraction to form copolymers, maintaining a reactiontimeV suiiicient to effect reaction of substantially all said more-highlybranched olefins charged, and separating a polymer fraction having a boiling range within themotor-fuel boiling range from the eflluent of said catalyst chamber.

2. A process for producing a hydrocarbon polymeric product from two different olen hydrocarbons. having low molecular weights, which comprises passing the less-reactive olefin into contact with a solid polymerization catalyst under reaction conditions such that said olen would polymerize with itself at only a relatively low rate and to a relatively small extent and such that the more reactive of the two olefins would mixture that is in contact with the catalyst is` greater than approximately 5 to l, whereby copolymerization between said olefins takes place forming higher-molecular-weight polymers, and subsequently separating a polymer fraction from at least a portion of the mixture which has been in contact with said catalyst.

3. A process for producing a hydrocarbon polymeric product from two separate olefincontaining hydrocarbon mixtures, the oleiins contained in the one mixture being generally more highly reactive than those contained in the other mixture, which comprises passing the first mixture containing the less-reactive olens into contact with a solid polymerization catalyst under reaction conditions such that a substantial portion of the individual olens contained therein would polymerize with themselves at only a relatively low rate and to a relatively small extent and such that a substantialportion of the individual more-reactive olefins contained in the second mixture would polymerize with themselves at a relatively high rate and to a substantial extent, adding at a plurality of successive points to the mixture in contact with said catalyst the second fraction containing the morereactive olefins in such amounts at the respective points that the molecular ratio oi the lessreactive olefins contained in the rst mixture to the more-reactive olefins contained in the second mixture throughout a substantial portion of the reaction mixture that is in contact with the catalyst is greater than approximately 5 to l, whereby copolymerization between the olens I in the two mixtures takes place forming highermolecular-weight polymers, and subsequently separating a hydrocarbon fraction containing the polymers vfrom. at least a portion of the mixture which has been in contactwith said catalyst.

d. A process for producing hydrocarbons having boiling points Within the motor-fuel boiling range from olefin hydrocarbons having low molecular weights, which comprises passing a rst hydrocarbon mixture comprising essentially straight-chain olefns having not less than three nor more than five carbon atoms per molecule under a pressure between approximately 200 and approximately 2500 pounds per square inch into a polymerization chamber containing a solid olefin-polymerization catalyst, maintaining reaction conditions in said chamber such that said straight-chain olelris are not rapidly nor extensively polymerized with themselves, passing to said polymerization chamber a second hydrocarbon mixture comprising essentially tertiary-base olens having not more than five carbon atoms per molecule, and adding isaid second hydrocarbon mixture to the reaction mixture in contact with said catalyst at a plurality of successive points in said polymerization chamber in such amounts at the respective points that the molecular ratio of unreacted straight-chain oleflns to unreacted tertiary-base olefins throughout a substantial portion of the reaction mixture in said polymerization chamber is at least approximately to l, whereby a copolymerization takes place betweenA straight-chain and tertiary-bas olens to form hydrocarbons having boiling points within the motor-fuel boiling range, and separating from at least a portion of the eilluent of said chamber a fraction containing hydrocarbons having boiling points Within the motor-fuel boiling range so produced.

5. A process for producing a hydrocarbon polymeric product having a boiling range within the motor-fuel boiling range from two separate and different butene fractions, one of which contains more isobutene than the other, which comprises passing the fraction containing the smaller proportion of isobutene under reaction conditions such that copolymerization between normal butenes and isobutene takes place readily but reaction between normal butenes takes place only to a minor extent over a solid. polymerization catalyst iii a catalyst chamberand adding the other fraction containing the greater proportion of isobutene to said catalyst chamber at a plurality of successive points in said catalyst chamber to react isobutene with normal bu- /to a minor extent over a solid vpolymerization catalyst in a catalyst chamber. and adding the other fraction containing the generally morehighly-branched olens to said catahrst cham.- ber at a plurality of successive points in said catalyst chamber to react olefns of the one fraction with olens of the other fraction to form copolymers, maintaining a. reaction time suflicient to effect reaction of substantially all said more-highly-branched olefins charged, separating a polymer fraction having a boiling range within the motor-fuel boiling range from the efiiuent of said catalyst chamber and sublecting said polymer fraction to nondestructive hydrogenation.

7. A process for producing hydrocarbons having boiling points within the motor-fuel boiling range fromolen hydrocarbons having low motenes to form copolymers, vmaintaining `a'reaction time suicient to effect reaction of substan.

rate and different olei'ln hydrocarbon fractions,

one of which contains oleiins that have generally more-highly-branched structures than those contained in the other fraction, which comprises passing the fraction containing the generally less-highly-branched olens under reaction conditions such that copolymerization between the more-highly-branched and less-highly-branched olens takes place readily but reaction between the less-highly-branched olens .takes place only lecular weights, which comprises passing a rst hydrocarbon mixture comprising essentially straight-chain oleiins having not less than three nor more than five carbon atoms per molecule under a pressure between approximately .20u and approximately 2500 pounds per square inch into a polymerization chamber containing a solid granular silica-alumina catalyst, maintaining reaction conditions in said chamber such that said straight-chain olenns are not rapidly noi` extensively polymerized with themselves, passing to said polymerization chamber a second hydrocarbon mixture comprising essentiaily tertiarybase olerlns having not more than live carbon atoms per molecule, and adding said'second hydrocarbon mixture to the reaction mixture in contact with said catalyst at a plurality oi' successive points in said polymerization chamber in such amounts at the respective points that the molecular ratiolof unreacted straight-chain olefins to unreacted tertiary-base oleiins throughout a substantial portion of the reaction mixture iir said polymerization chamber is at least approximately 5 to 1, whereby a copolymerization takes place between straight-chain and tertiary-base olens to form hydrocarbons having boiling points within the motor-fuel boiling range, and separating from at least a portion of the eiiluent of said chamber a fraction containing hydrocarbons having boiling points Within the motor-fuel boiling range so produced and subjecting said hydrocarbons to nondestructive hydrogenation.

8. A process for producing a predominantlyparafnicpremium motor fuel from two separate and dilerent butene fractions. one of which contains more isobutene than the other, which comprises passing the fraction containing the smaller proportion of isobutene under reaction conditions such that copolymerization between normal butenes and isobutene takes place readily but reaction between normal butenes takes place only to a minor extent over a solid polymerization` catalyst in a catalyst chamber and adding the other ing boiling points within the motor-fuel boiling range, which comprises passing a hydrocarbon mixture containing straight-chain and tertiarybase olens having not more than five carbon atoms per molecule to a fractionating means, withdrawing from said .fractionatlng means -.a stream of hydrocarbons' comprising .straightchain and tertiary-base olefins having not more than iive carbon atoms per molecule, circulating an endless cycle of. hydrocarbons.. intoand. 4out of contact with a solidpolymerization catalyst contained in. a reaction, chamber, maintaining reaction conditions in said chamber such that straight-chain olens are not rapidlynor extensively polymerized with themselves andsuch that tertiary-base olefins having not more than ve carbon atomsper molecule would ,be substantially polymerized with themselves, the pressure being between approximately 200 and approximately 2500 pounds per square inch and the temperature between approximately 25v and approximately 320 C., adding said stream` of hydrocarbons tov 10. A process for the production of hydrocarbons having .highly branched structures ,and hav-l ing boiling points within the motor-fuel boiling,

mixturecontaining straight-chain and tertiarybase olelinshaving less than six carbon atoms per molecule and other hydrocarbons to a fractionating column, withdrawing from said fractionatingcolumn al stream of hydrocarbons oomprising straight-chain and tertiary-base oleflns having less than six carbon atoms per molecule and..in a molecular-.ratio of staright-chain to tertiary-base olefins oi.' approximately 1 to l, circulating an .endless cycle of a mixture of hydrocarbons substantially entirely in liquid phase into and: out of contact with a solid polymerization catalyst situated within, a reaction chamber, maintaining within said reaction chamber a reaction temperature not in excess of approximately 260C. and a reaction time such that tertiarybase -olefins having less than six carbon atoms per molecule would be substantially polymerized wlthfthemselves, adding said stream of hydrocarbons to said endless cycle of hydrocarbons in such proportions 1that the ratio of straight-chain oleflns-to tertiary-base oleiins having less than six carbon atoms per molecule is maintained between approximately 5 to 1 and approximately4 19 tol, adding-normally liquid hydrocarbons in an amount such that a liquid phase is maintained in said reaction chamber, withdrawing from said endless cycle a portion thereof, contacting said portion A.with a second polymerization catalyst under reaction conditions such that substantially all of the original oleflnsg having less than six carbon atoms per molecule 'are polymerlzed, passing the ellluent from said secondvpolymerization catalyst to said fractionating column and withdrawing from said column a hydrocarbon iraction containing olefin polymers so produced.

FREDERICK Iii.'V FREY.

CERTIFICATE OF CORRECTION.

Patent No. 2,577 ,M111 June 5, 1915.

FREDERICK E. FREY.

It is hereby certified that error appears in the printed specification 'of the above numbered patent requiring correction as follows: Page 2, first column, line 52, for "higfihly" read --highly--g page 5, second column, line 72, for "elefin" read olefin; page lL, first column, line 12, after the word "so" ins ert --on; page lO, first column, line 29, before "olefins" insert original; and that the said Letters Patent should be read with this correction therein that the same may conform to the record, of the case in the Patent Office.

Signed and sealed this 2nd day of October, A. D. 19h15.

Leslie Frazer (Seal) First Assistant commissioner of Patents.. 

